The present invention relates to a gauge for measuring the height of a bead of adhesive used in the assembly of components.
Many components are assembled together with the use of adhesives or glues. Robotic machines are commercially available to apply controlled amounts of adhesive during assembly processes. Such machines inject or apply adhesive so that a layer or “bead” of adhesive is formed on an outer surface of the component or components to which the adhesive is applied. To achieve a proper assembly, it is often necessary to use a proper amount of adhesive, and to assure quality assemblies it is necessary to periodically measure the amount of applied adhesive to insure the correct operation of the adhesive applying machine. Various methods and tools have been used to measure the height of an adhesive bead on a part, such as machine vision systems and laser triangulation systems. But such systems are expensive and unreliable. Adhesive bead height has also been measured with a commercially available digital height gauge which has a measuring probe. However, with this type of gauge it is nearly impossible to measure the height of a soft wet bead of adhesive, because, when positioning the measuring probe, the probe may be above the bead or the probe may plunge into the bead, creating high measurement error.
A Technical Data Sheet for LOCTITE® adhesive Product 5910 describes a “PTFE block” which can be used to determine the depth of cure of an adhesive in a given amount of time. The block includes a channel which gradually increases in depth from 0 to 10 millimeters. The channel is filled with adhesive and allowed to cure for a certain time period, after which the adhesive is peeled away from the channel. The channel depth at the point where the adhesive remains is the cure depth for that particular cure time. However, because adhesive is applied to the tool and not applied by the production adhesive applying machine, and is not applied to a sample part, this tool cannot be used to determine whether an adhesive applying machine is set up properly to apply an adhesive bead with a proper height.